Abbreviation of the phrase "Bitching in Range." To talk negatively of a certain person/persons, when said party may be present within a distance capable of hearing such accusations. This often leads to an awkward silence, and a brief wave of severe guilt.
Adopted by a clan called 'The Cider-Riders' , the phrase has spread to mainstream use by the students of KEGs, which is a college in a town somewhere near Coventry.

'Remember to always check for BIR prior to bitching.'